Unique Concepts and Features of Seismic Isolation Systems

Abstract

This book includes results achieved by the author in the field of seismic isolation during the period of time from 1993 to 2022. To date there are 56 seismic isolated residential, medical, hotel, business centre, airport, and school buildings in Armenia newly constructed or retrofitted by base or roof isolation systems. The number of seismically isolated buildings per capita in Armenia is one of the highest in the world, second after Japan. Also, the seismic isolation laminated rubber-steel bearings (SILRSBs) different by their shape, dimensions, and damping (low, medium, and high) were designed and more than 5500 SILRSBs were manufactured in the country, tested locally, and applied in construction. Large numbers of remarkable projects on construction of new and retrofitting of existing buildings by base or roof isolation systems invented by the author are described to demonstrate the unique experience accumulated in Armenia. Exceptional features of the seismic isolation systems give the opportunity to apply them to steel, stone, reinforced masonry, reinforced concrete frame, braced frame, and large panel (1 to 20 stories) buildings with regular or asymmetric plans and to the cultural heritage structures. In seismic isolated buildings the approach suggested by the author on installation of the clusters of small SILRSBs instead of a single large bearing was used. Analyses of base isolated buildings carried out by the Armenian Seismic Code and the time histories show that structural elements below and above the seismic isolation planes are working mainly in the elastic phase. Input acceleration of 0.4g-0.5g at the foundation bed gets damped about 2.5-3.0 times in the superstructures, confirming the high effectiveness of the created unique structural concepts. Comparative analyses have shown that suggested seismic isolation strategies are reducing the consumption of concrete by about 2 times and steel – 2.7 times, and, finally, the cost of construction of new seismic isolated buildings on 35-40% in comparison with the cost of conventional construction. This includes the cost of manufacturing and installation of SILRSBs. Unique seismic isolation strategies developed by the author are also reducing the cost of retrofitting by base or roof isolation of existing buildings from 3 to 5 times in comparison with the cost of conventional strengthening of existing buildings. Operations on retrofitting by the invented technologies are made without interruption of the use of existing buildings, without eviction of people. The book also describes dynamic testing of the 9-story full-scale building using powerful vibration machine installed on the top of the building equipped by roof isolation system in the form of an Additional Isolated Upper Floor acting as a tuned mass damper. Extensive results on testing of SILRSBs for bridges and various buildings using developed by the author testing facilities are presented together with statistics on manufacturing of bearings by different Armenian companies and with proposal on more accurate determination of damping factors for SILRSBs. Stages of development of the Code for design of seismic isolated buildings are discussed and the well illustrated information on the author’s activities related to the worldwide dissemination of knowledge on the created by him and extensively implemented unique seismic isolation concepts is given.